The oceans represent a major sink for atmospheric carbon dioxide and one of the most important topics of oceanographic research is understanding its fate and in particular, the role of marine biological processes in carbon cycling. Within the oceans, organic matter is produced primarily in the euphotic zone, a region extending to ~200 m depth where sunlight is available to support photosynthesis. Oceanographers study the production and cycling of organic matter in this region extensively using a combination of remote sensing with satellites, continuous observations from surface moorings, and intense ship-based studies.

Biological productivity in the upper ocean leads to a continual ‘rain’ of organic debris into the underlying deep ocean but its fate in this region is less well known because of the logistical difficulties of conducting long-term experiments in this environment. Until recently, deep ocean ecosystems were thought to be only weekly coupled to variations in surface productivity because of the slow sinking rates of detritus and the effect of remineralization.

Carbon Fluxes in Deep-Sea Communities

It is now known that organic matter can reach the seafloor at depths of >5000 m quickly leading to a rapid response by abyssal communities. This advance has led to many additional questions concerning the dynamics of this response and its linkages to various scales of variability in the upper ocean. For example, it is not known if deep-sea communities respond to changes in the flux of organic carbon by a corresponding change in productivity of all biotic components or if changes in flux are absorbed less equitably.

Experiment Design

The OOI cabled observatory will provide the infrastructure to conduct long-term studies of the relationships between temporarily varying detrital carbon fluxes and benthic communities. Core measurements of oceanographic parameters (currents, temperatures, oxygen and suspended sediment) and energy flux (organic carbon input) will be combined with biological measurements including periodic imaging of deep-water and seafloor communities, measurements of the rate of oxygen consumption, carbon remineralization and nutrient fluxes, and modern microbial sampling and in-situ analysis. Mobile benthic rovers will be used to extend the spatial coverage of studies.

Parts of this page were extracted from RECONN: REgional Cabled Observatory Network (of Networks), Report of the Cabled Regional Observatory Workshop, October 7-10, San Francisco, CA 2003.